Gas combustion turbine engines are used for generating power in a variety of applications including land-based electrical power generating plants. Gas turbine engines are known to produce an exhaust stream containing a number of combustion products. Many of these byproducts of the combustion process are considered atmospheric pollutants. Of particular concern is the production of the various forms of nitrogen oxides collectively known as NOx. It is known that NOx emissions from a gas turbine increase significantly as the maximum combustion temperature rises in a combustor of the gas turbine engine as well as the residence time for the reactants at the maximum combustion temperature within the combustor.
U.S. Pat. No. 6,047,550 discloses an axially staged combustion system for a gas turbine engine. It comprises a premixed combustion assembly and a secondary fuel injection assembly located downstream from the premixed combustion assembly. The premixed assembly comprises start-up fuel nozzles and premixing fuel nozzles. The secondary fuel injection assembly illustrated in FIG. 2 of the '550 patent includes eight fuel/air injection spokes, with each spoke having a plurality of orifices. Mixing of the fuel provided by the secondary fuel injection assembly is believed to be limited due to the small number of fuel/air injection spokes and orifices provided in those spokes. Limited mixing of fuel with air may result in rich fuel zones causing high temperature combustion zones, e.g., 2000 degrees C. and, hence, excessive NOx emissions.